1. Field of the Invention
The present invention relates to a hand tool and, more particularly, to an oil core wrench.
2. Description of the Related Art
A conventional oil core wrench 1 in accordance with the prior art shown in FIGS. 1-3 comprises a threaded rod 12, a non-rotation member 11 mounted on the upper end of the threaded rod 12 by a screw member 111, a rotation handle 2 mounted on the lower end of the threaded rod 12 by a screw member 21 which is screwed into a screw bore formed in the lower end of the threaded rod 12, a nut 13 screwed onto the threaded rod 12, and a clamping member 14 extending through the non-rotation member 11 and connected with the nut 13. The clamping member 14 has two distal ends extending through the non-rotation member 11 and secured to the nut 13 by two screw members 132. Each of the two distal ends of the clamping member 14 is provided with an aperture 141 to allow passage of one of the two screw members 132. The nut 13 is provided with two screw holes 131, and the two screw members 132 are respectively screwed into the two screw holes 131 of the nut 13 so that the clamping member 14 is secured to the nut 13. In operation, the clamping member 14 is mounted on an outer diameter of an oil core. When the rotation handle 2 is rotated along a vertical axis, the threaded rod 12 is rotated so that the nut 13 is moved downward, and the clamping member 14 is also moved downward to shorten the inner diameter of the clamping member 14. When the outer diameter of the oil core is sandwiched and clamped between the inner diameter of the clamping member 14 and the top of the non-rotation member 11, the rotation handle 2 stops rotating. When the rotation handle 4 is turned along a horizontal axis, the threaded rod 12 and the non-rotation member 11 are turned in concert with the rotation handle 2 so as to rotate the oil core. Thus, the oil core wrench 1 can drive the oil core to rotate in the clockwise direction so as to tighten the oil core or to rotate in the counterclockwise direction so as to loosen the oil core. When the oil core is mounted in a narrow region, such as an engine, there is not much space to allow movement of the rotation handle 2, so that it is necessary for the oil core wrench 1 to drive and rotate the oil core in a oneway manner. However, the conventional oil core wrench 1 does not have a oneway operation function so that the conventional oil core wrench 1 cannot be operated easily and quickly in the narrow region, thereby greatly causing inconvenience to the operator and increasing the working time.